Oil recovery using steam-chemical drive fluids

ABSTRACT

An improved method for recovering hydrocarbons from underground formations which contain both hydrocarbons and a polyvalent salt formation water comprises injecting into said formation a steam composition containing a basic salt and a sequestering agent, the steam condensate of said steam composition having a pH of at least 8, said steam composition capable of forming an emulsion mobility front and a steam drive.

United States Patent Zwicky et al.

[54] OIL RECOVERY USING STEAM- CHEMICAL DRIVE FLUIDS [72] Inventors: Robert W. Zwicky, 5152 Nesbitt Rd., Calgary 47, Alberta; Robert M. Gies, 10 Vartown PL, Calgary 45, Alberta, both of Canada [22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,669

[52] US. Cl ..l66/272 [51] Int. Cl. ..E2lb 43/24 [58] Field of Search 166/270, 272-275, 166/303 [56] References Cited UNITED STATES PATENTS 2,813,583 11/1957 Marx et al ..l66/272 X 3,258,072 6/1966 Froning ..166/275 X 3,414,053 12/1968 Treiber et al. ..166/273 2,288,857 7/1942 Subkow ..l66/272 X 3,193,009 7/1965 Wallace et al. ..166/272 3,221,813 12/1965 Closmann et al. .....166/272 X 3,373,808 3/1968 Patton ..166/275 3,490,532 1/1970 Carlin ..l66/272 X 3,532,165 10/ 1970 Raifsnider 1 66/270 3,572,838 3/1971 Templeton ..l66/272 UX OTHER PUBLICATIONS Frick, Thos. C. Petroleum Production Handbook, Vol. II, N.Y., McGraw- Hill, 1962, page 41- 68.

Primary Examiner-Stephen J. Novosad Att0rneyGeorge G. Pritzker and Harold L. Denkler [57] ABSTRACT An improved method for recovering hydrocarbons from underground formations which contain both hydrocarbons and a polyvalent salt formation water comprises injecting into said formation a steam composition containing a basic salt and a sequestering agent, the steam condensate of said steam composition having a pH of at least 8, said steam composition capable of forming an emulsion mobility front and a steam drive.

3 Claims, No Drawings OIL RECOVERY USING STEAM-CHEMICAL DRIVE FLUIDS BACKGROUND OF THE'INVENTION The present invention relates to a method of recovering highly viscous essentially immobile hydrocarbons from underground formations containing such hydrocarbons in association with connate water containing polyvalent alkaline earth metal salts, with a steam drive containing a basic salt and a sequestering agent in amounts such that the resultant steam condensate in the formation has a pH of at least 8 and is capable of forming an emulsion front and thereby increasing and maintaining the mobility of the essentially immobile hydrocarbon so as to effect improved hydrocarbon recovery.

The use of various thermal drives to impart mobility to essentially non-flowable hydrocarbons as encountered in some underground formations containing tar sands, oil sands or oil shales for the purpose of effecting hydrocarbon (oil) recovery, is well known in the art. One of the most preferred thermal drive or flooding oil recovery methods is the use of steam drives as described in US. Pat. Nos. 2,813,583; 3,193,009; 3,279,538; 3,354,958 and 3,410,345 or Canadian Pat. Nos. 639,050 and 560,117. In general, the art relating to use of steam as a thermal drive is directed to pretreating the water used to form the steam so as to remove undesirable components therefrom as described in US. Pat. No. 3,193,008 or using steam in combination with another fluid drive such as water, gases formed by in-situ combustion, and the like. Generally, where a mobility control front is established in order to prevent fingering of the steam and improve mobility of the non-flowable hydrocarbon, the front is of such a nature as to resist formation of emulsions since on recovery they are difficult and costly to break.

EMBODIMENT OF THE INVENTION In accordance with'the present invention, the above disadvantages of the known method of hydrocarbon (oil) recovery can be obviated and an improved and high degree of recovery of hydrocarbons from a hydrocarbon and formation water containing underground formation can be achieved by utilizing as the thermal oil recovery drive, steam containing an alkali metal carbonate and a sequestering agent, said additives being present in amounts sufficient to give the resultant steam condensate a pH of at least 8 and capable of chelating or precipitating polyvalent alkaline earth metal ions from solution in the formation water and said steam condensate carbonate salt-sequesterant composition forming an emulsion mobility front between the non-flowable or immobile hydrocarbon and the steam drive capable of increasing and maintaining the non-flowable hydrocarbons in a flowable or mobile state so as to be effectively recoverable via a system of injection and production wells.

The alkali metal carbonates used in the steam drive include sodium, potassium, lithium and/or ammonium carbonate or bicarbonate and are added to the steam in an amount sufficient to form a condensate in the formation having a pH of at least 8 and preferably between 8 and 12. Preferred carbonate is sodium carbonate and the pH being between about 8 and 10.

As used herein the term sequestering" means to set apart, to put aside, or to separate as by chelating or precipitating. The sequestering agent can be any additive capable of chelating or precipitating the polyvalent alkaline earth metal ions in the formation or connate water and includes alkali metal sulfates, sulfites, polyphosphates, polyamine polyacetates, e.g., sodium and/or potassium sulfates and/or sulfites or polyalkylene polyamine acetates, e.g., diethylene triamine acetate and the like.

The presence of the carbonate and sequestering agent function synergistically in the steam drive or steam condensate to form an emulsifiable mobility front capable of preventing steam fingering and imparting mobility to the non-flowable hydrocarbons and which on recovery is easily broken or separated into its components.

The steam-additive containing drive of the present invention is particularly effective in aiding in recovery of oil or tar, e.g., heavy oils, or tars (called tar hereinafter) from reservoirs such as the Peace River Bullhead .oil sands of northern Alberta. Thus, when using the steam containing sodium carbonate with specific sequestering agents such as sodium sulfate or sodium sulfite as a drive fluid, the tar is readily recovered from an injection and/or production well(s). This type'of drive promotes the formation of tar-inwater emulsions near the point of initial contact between the steam and tar thereby increasing and maintaining the mobility of the tar. The effect is both direct action of the chemicals on the tar and indirect by precipitating polyvalent alkaline earth ions from solution in the formation water. The concentration of sodium carbonate and other additives should be sufficient to give the steam condensate in the formation a 8.0 of 9.0 to 10.0.

I SPECIFIC EMBODIMENT OF THE INVENTION In a normal or conventional steam drive, once the tar is heated to a point where its viscosity decreases sufficiently to become mobile at the initial point of contact between tar and steam, there remains the problem of keeping the tar mobile as the stream in which it is moving cools. Having the tar entrained in a tar-in-water emulsion at or near the initial contact site by means of the steam composition drive of the present invention ensures its continued mobility at decreased temperatures.

The formation waters of tar sands such as the Peace River Bullhead formation, contain polyvalent alkaline earth ions-specifically calcium and magnesiumwhich inhibit emulsification. Sodium carbonate and sequestering agents are added to the steam for the following reasons:

]. To precipitate calcium and magnesium ions from the formation water by forming insoluble carbonates or sulfates.

2. To raise the alkalinity of the formation liquids.

3. To lower the surface tension between the heavy oil or tar and the steam condensate.

Each of these factors help promote the formation of tar-in-water emulsions.

Sodium carbonate in particular is used as it creates a weakly alkaline solution when dissolved in water which is much less corrosive to the formation than sodium increasing the effectiveness of the sodium carbonate. It

is a matter of relative economics and prior additional uses (such as water treatment) which will dictate the best ratio of chemical additives.

We claim as our invention:

1. A method of recovering hydrocarbons from an underground tar sand containing formation water and containing non-flowable hydrocarbons in their original form comprising the steps of:

a. arranging at least one injection well and at least one production well penetrating into said formation and communicating with each other;

b. injecting through one of the injection wells and into the tar sand formation containing hydrocarbons and formation water, steam containing an alkali metal carbonate and a sequestering agent in amounts sufficient to give the steam condensate a pH of at least 8;

c. continuing injection of the steam composition (b) until an emulsion front is established; and

d. recovering flowable hydrocarbons via a production well.

2. A method of recovering hydrocarbons from an underground tar sand formation containing formation water having polyvalent ions comprising the steps of:

a. arranging at least one injection well and at least one production well penetrating into said formation and communicating with each other; b. injecting through one of the injection wells and into the tar sand formation containing hydrocarbons and formation water having polyvalent ions, steam containing a mixture of alkali metal carbonate and alkali metal sulfate in amounts sufficient to give the steam condensate a pH of at least continuing injection of the steam composition (b) until an emulsion front is established; and

d. recovering flowable hydrocarbons via a production well.

3. A method of recovering hydrocarbons from an underground tar sand formation containing formation water having polyvalent ions comprising the steps of:

a. arranging at least one injection well and at least one production well penetrating into said formation and communicating with each other;

b. injecting through one of the injection wells and into the tar sand formation containing hydrocarbons and formation water having polyvalent ions, steam containing a mixture of sodium carbonate and sodium sulfate in amounts sufficient to give the steam condensate a pH of at least 8;

c. continuing injection of the steam composition (b) until an emulsion front is established; and

d. recovering flowable hydrocarbons via a production well. 

2. A method of recovering hydrocarbons from an underground tar sand formation containing formation water having polyvalent ions comprising the steps of: a. arranging at least one injection well and at least one production well penetrating into said formation and communicating with each other; b. injecting through one of the injection wells and into the tar sand formation containing hydrocarbons and formation water having polyvalent ions, steam containing a mixture of alkali metal carbonate and alkali metal sulfate in amounts sufficient to give the steam condensate a pH of at least 8; c. continuing injection of the steam composition (b) until an emulsion front is established; and d. recovering flowable hydrocarbons via a production well.
 3. A method of recovering hydrocarbons from an underground tar sand formation containing formation water having polyvalent ions comprising the steps of: a. arranging at least one injection well and at least one production well penetrating into said formation and communicating with each other; b. injecting through one of the injection wells and into the tar sand formation containing hydrocarbons and formation water having polyvalent ions, steam containing a mixture of sodium carbonate and sodium sulfate in amounts sufficient to give the steam condensate a pH of at least 8; c. continuing injection of the steam composition (b) until an emulsion front is established; and d. recovering flowable hydrocarbons via a production well. 